As demands on wireless and other electronic devices evolve there is an increased need for electronic devices that can provide higher performance at high frequency. One way of meeting these requirements is to create devices using T-gates. The T-gate is a gate conductor structure for a semiconductor device, such as a Gallium Nitride High Electron Mobility Transistor (GaN HEMT). For high performance such as a high operating frequency and a high transconductance, the stem of the T-gate is narrow. For high switching speeds the wings (or top) of the T-gate are wide. The result is a gate conductor structure that provides the high performance and high frequency demanded in electronic devices such as high performance commercial communications and military systems.
The demand for higher performance conductor structures leads to a more demanding semiconductor fabrication process. Particularly in the area of fabricating T-gates using bi-layer resists, there cannot be any spurious material extending from a T-gate to a source or drain ohmic contact. Electron beam exposure and development may cause stress cracks in a bi-layer resist. Fabricating a T-gate using a cracked resist may lead to spurious material extending from these cracks. Such spurious material may cause the T-gate to short to an ohmic contact. Even if the spurious material does not cause the T-gate to short, the spurious material may cause electrical breakdown of HEMT devices.
Therefore, there is a need in the art for an improved method and system for fabricating T-gates such that electron beam exposure and development does not cause stress cracks in a resist, and spurious material does not extend from a T-gate to a source or drain ohmic contact.